Apparatus for advancing well bores by explosives



May 25, 1954 w. G. swEETMAN 2,679,380

APPARATUS F OR ADVANCING WELL BORES BY EXPLOSIVES y Filed Oct, 8, 1948 3ShiDS-ll I wlLLlAM migiam FIG. 2y Z0 ATTORNEY May 25, 1954 w. G. swEETMAN APPARATUS FOR ADVANCING-WELL BORES BY EXPLOSIVES 3 Sheets-Sheet 2 FIG. B'A

Filed Oct. 8, 1948 INVENTOR. WILLIAM G. SWEETMAN BY QA-0&4

ATTORNEY May 25, 1954 APPARATUS FOR ADVANCING WELL BORES BY EXPLOSIVS Filed Oct. 8, 1948 3 Sheets-Sheet 3 Ii la FIG. 7

WlLLIAM G. SWEETMAN INVENTOR.

ATTORNEY vable by conventional methods.

Patented May 25, 1954 lUNITED STATES ATENT OFFICE APPARATUS FOR ADVANCING WELL BoREs BY ExrLosIvEs William G. Sweetman, Houston, Tex. Application October 8, 1948, Serial No. 53,478

3 Claims.

This invention relates to drilling of wells with explosives and particularly to advancing the bore of a well through hard earth formation or hard extraneous objects which may be present in the path of the drill and which are not readily drill- This invention is a continuation-in-part of my co-pending application, Serial No. 709,246, filed November 12, 1946, for Method and Apparatus for-Cutting Inside a Well, now Patent No. 2,587,244, February 26, 1952;,-

In conventional well drilling methods, such as the rotary method, very hard rock strata such as chert or granite, for example, are frequentlyv encountered through Which it is extremely diicult to advance the bore hole by means of conventional drilling tools. Very often a matter of days may be required' to drill as little as a few inches, even when employing the most modern types of rock bits and other conventional tools and methods. The bits will dull extremely rapidly, so that the drill stem must be withdrawn and returned tothe well'at very frequent intervals for replacement of the bit with consequent delay and great expense, not only in the loss of drilling time but also in the cost of repair and replacement of the bits and@ other tools. Many thousands of 'dollars may be expended in the drilling of only a very few -feet of such hard strata.

Drilling through some formations such as shales, and particularly heaving or sloughing.;j

shales or which are subject to swelling or crumbling, diculty is encountered in advancing the well bore particularly where water is employed during the drilling operation or is encountered during such operation, resulting in heaving org sloughing of the formation into the hole, particularly when the drill pipe is withdrawn.

Another similar diculty frequently arises as a result of the loss or dropping of a part of the metallic drilling tools into the bottom of a Wells;-

Often, for example, the cones of a rotary bit will break loose from the bit stem and remain in the bottom of the well. These are usually constructed of the very hardest types of metal and if they cannot be lished out, are practically iin-- possible to drill out and may even require sidetracking of the well bore which is an expensive and time-consuming operation.

Casing plugs, cementing shoes and oat shoes, which are generally employed during the course of drilling, must be drilled out, at least as to the parts thereof projecting inwardly beyond the interior of the casing. Accordingly it has been necessary to construct such parts of materials other than steel, namely; a more frangible ma- 2 terial such as cast iron, aluminum alloys, plastics and even cement. The employment of such materials however is not `only costly, but involving as it does materials of relatively low strength, are less reliable than if those parts could be constructed of steel.

In certain areas Where the producing formations are found beneath a hard strata, commonly known as the cap-rock, a common practice is to drill the well to the top of the cap rock by the usual rotary method, and then substitute for the rotary drill, a percussion type drill and complete the well through the cap rock by the so-called cable-tool method of drilling. This requires substitution of a new set of drilling tools and is a relatively time-consuming and expensive operation.

Advancing the bore of a well by shooting with explosives is not practical because of the lack of control of any directive action of explosives generally. Moreover this results in a shattering of the wall, which is undesirable, and where a casing is in place it involves destruction of the casing in the region Where the explosive is used.

Generally stated, and in accordance with iltrating jet inside of the well and adjacent its bottom, by detonating a chemical charge and by converging the resultant gases to a relatively sharp focus or into a relatively narrow column, and directing the jet or column downwardly against the well bottom. An apparatus for advancing the well bore can be in the form of a tool comprising a carrier designed for placement inside of the well and adjacent its bottom, and a detonatable chemical charge on the carrier having means for so converging and directing the gases downwardly in the manner described. The detonatable chemical charge as described' is of the hollowed charge form with its hollow directed downwardly and spaced from thebottom of the carrier a predetermined distance, so that when the bottom or nose of the carrier is located adjacent the well bottom it will secure convergence of the jet in that region. It will be understood that the expressions bottom of the Well and objects which are not readily drillable by conventional methods, or which can be readily advanced in accordance with this invention.

An important object is the provision of an apparatus for advancing a well bore by the ernploynient of detonating explosives.

A further object is the provision of an apparatus for advancing a well bore by controllably directing the explosive force of a detonating chemical charge against the bottom of a well bore to penetrate the material composing the same.

Other and more specific objects and advantages of this invention will become apparent from the following detailed description when read in conjunction with the accompanying drawings which illustrate a number of embodiments in accordance with this invention.

In the drawings:

Fig. 1 is a view showing the drilling apparatus in place in a well bore preparatory to advancing the bore through a hard earth formation;

Fig. 2 is a view similar to Fig. 1 illustrating the appearance of the well bore and drilling apparatus after operation;

Figs. 3, 3A and 3B, together, comprise a longitudinal sectional view through the drilling apparatus;

Figs. 4, 5 and 6, are cross-sections taken along lines 4-fi, 5-5, and 5--6, respectively, of Fig. 3; and

Figs. 7 and S are views similar to Fig. 1, illustrating additional embodiments of this invention.

Referring to the drawings, the apparatus, in accordance with an illustrative embodiment of this invention, includes a firing head, indicated generally by the numeral l0, which comprises a generally cylindrical casing 2li which is closed at its lower end by means of an integral nose piece 2|, which may be of conical, tapered or rounded formation to serve as a guide for the casing. An annular shoulder 22 is provided inside the bore of casing 2li longitudinally spaced from nose piece 2l. The upper end of casing 20 is provided with a removable closure sion 24 adapted to be inserted snugly inside the bore of casing 2i) and provided with an annular flange adapted to seat on the upper rim of casing 2D when extension 2d is inserted therein. A plurality of set screws 25 extend radially through the wall of casing 2e into locking engagement with extension 24 to thereby lool; closure 23 to casing 20. A compressible packing element 26, such as a conventional O-ring, is installed between the adjacent faces of extension 2li and casing 2G to form a fluid-tight seal therebetween. An explosive charge 2'! is packed into the interior of casing 2l! to fill the space between shoulder 22 and closure 23, and is provided in its lower face with a hollow, as at 2S, which is generally conical in form but which may be of other hollow shape, which in axial cross section, will be semicircular, elliptical and the like, and symmetrical with respect to the axis of the charge. Hollow 28 is provided with a liner member 29 lying against the hollow and of corresponding shape and having its outer periphery adapted to seat on shoulder 22. A charge of booster explosive Se is embedded axially in the upper end of the main charge 21.

Explosive charge 21 and booster explosive 30 are chemical substances of the type generally designated as a detcnating explosive which, upon detonation, decompose very rapidly to gencrate gaseous decomposition 23 having a tubular exten-I products which` are capable of attaining extremely high velocities. particularly when controlled and directed, as will be hereinafter described. Numerous chemicals of this character are available for use in accordance with this invention including such materials as penta-erythritol, tetranitrate (PETN), tetryl, Pentolite (50% PETN and 50% TNT), trinitrotoluene (TN') amatol, Cyclonite, retrytol (60% tetryl and 40% TNT), and many others well known to those familiar with such detonating chemicals. These chemicals may be employed in cast or compressed solid form, but may be employed in the form of plastic or gelatinous masses which may be readily molded or packed into the desired shape, and may be used individually or as blends of two or more of them in suitable proportions, and may include suitable detonatable plasticizers.

Liner member 29 is preferably made of thin metal such as steel or copper and by its shape and thickness serves to converge or focus the gases generated by detonation of the explosive charge into a jet or column, the cross section of which will initially be substantially that of the charge, and which will be maintained in tapering form for a distance depending upon the angle and thickness of the liner, the mass and character of the charge and other factors, as described in greater detail in my co-pending applications Serial No. 703,655, led 'October 16, 1946,-now

` Patent No. 2,587,243, February 26, 1952, and Serial No. 709,246 mentioned above.

Extending from the upper face of closure 23 is a generally cylindrical boss 3i, having an axial bore 32 communicating with the interior of casing 29 through closure 23. A fuse element, indicated generally by the numeral 33, of generally conventional form, is installed. in bore 32 in detonating relation to the booster and main explosive charges. Fuse element 33 comprises a cylindrical electrical detonating cap 3d, installed in the end of a tubular bushing which is adapted to be screwed into the upper end of boss 3l. An electrode 35 extends through the bore of bushing 35 'and is suitably insulated therefrom. The inner end of electrode 3S is connected to one of the wire leads 3l of the detonating cap, the other lead being suitably grounded by being connected to the bushing which is, in turn, in electrical contact with the other metallic parts of the device.

Boss s i carrying fuse element 33, extends into the lower end of a connector sleeve 33 and is connected thereto by means of set screws 39 which extend radially through the wall of sleeve 38 into grooves iii in the surface of boss 3l. A resilient ring il encircles boss Si and is positioned between the lower end of sleeve 33 and the upper surface of closure 23. An elongated metal tube 42 has its lower end seated in the upper end of the bore of sleeve 33 and connected thereto by means of set screws i3 extending radially through registering openings in the adjacent walls of sleeve 38 and. tube 4t2. rIhe upper end of tube @2 is connected by means of set screws is to a tubular socket member l5 having an axial bore 46 registering with the bore of tube 52. Socket member l5 has an internally threaded box 11 at its upper end and an electrical contact i8 is seated in the bottom portion of box di. An electrical conductor lead 49 is connected to contact 63 and is threaded through the registering bores of socket members 45, tube 42 and sleeve 3S when its lower end is connected to the upper end of electrode 36. Tube 42 comprises a shocl; absorber element, which is designated generally byvnuineral l i, the function of which will be described vin greater detail hereinafter.

Vmetal and adapted to impart substantial weight to the apparatus. Body is provided at its lower end with an externally threaded pin l which is adapted to be screwed into box 471. An axial passageway 52 extends entirely through body il!) and has seated in the lower end thereof an electrical contact 53 which is adapted to engage contact 48 when pin 5l is screwed into box 41. The opposite end of body 5t is provided with a threaded pin 54 through which bore 52 extends and has mounted therein an electrical contact 55 which is connected to contact 53 by means of a suitably insulated conductor lead 56. Pin 54 is adapted to be screwed into a threaded box 5l carried by a sub element i3 provided with a cooperating electrical contact 58 engageable with contact 55 when `pm 54 is screwed im@ box 5i. Contact 5s is connected by a conductor lead 59 threaded through sub I3 and adapted to be electrically connected in a similar manner at its upper end to a conventional electrical plug lll adapted to be inserted into the upper end of sub I3. Plug i4 is carried by the end of a lowering cable l 5 through which an electrical conductor lead l5 is threaded and through which electric current may be transmitted to lead 59 and thence through the other electrical connections above described to fuse element lt will be understood that cable l5 extends to the surface of the well in which the apparatus is to be operated and is employed to raise and lower the apparatus as required. It will also be understood that conductor lead I6 will be connected to a suitable and conventional source of electric current (not shown) for supplying electrical current to the apparatus.

The above-described apparatus is employed in the following manner, reference being had particularly to Figs. l and 2: The apparatus, constructed and assembled as previously described, will be lowered into a well bore I7 in which has been encountered, for example, a hard rock formation, indicated at 53, through which it is desired to advance the bore hole. The apparatus will be lowered until the nose of firing head It is in contact with or immediately above the bottoni of the well formed by formation I8 and exy plosive charge 2l will be set off by supplying ring current from the surface through conductor lead it to fuse element 33. The resulting detonation of cap 53d will set oif booster explosive Si! which will, in turn, detonate the main charge 22'. By providing hollow 28 and liner 29 in the lower end of explosive charge 2l, the explosive force generated by the detonation of explosive charge 2l will be concentrated into a generally cylindrical column of force the major portion of which will be directed downwardly along the axis of the charge and will strike the face of formation I8 and pierce the same for a distance depending in general upon the mass and character of the explosive charge, the shape of the hollow, the character of lining 29, and the distance between the hollowed face of the charge and the face of the formation. The general shape and appearance of the hole made by the directed explosive force is illustrated in Fig. 2. Casing and the other parts of the firing head will normally be made of an easily shatterable metal such 'as aluminum or magnesium or alloys thereof or vthe like, particularly Where hydrostatic fluids are .present in the well and the casing must be made Vlsuinciently strong to withstand the pressures thereof. In the absence of such fluids, other materials such as rigid plastics may be employed with success. Shock absorber Il, comprising in general tube 42 will be made of a relatively ilexible metal such as aluminum or copper tubing,

- which'is adapted to absorb the recoil of the explosion by collapsing and twisting in the manner illustrated in Fig. 2. By thus absorbing the recoil, the upper part of the apparatus such as socket member i5, sinker bar l2, sub I3 and plug i4 will remain undamaged and may be withdrawn from the well and re-used lor connectlon to a new tube i2 and ring head IG. It will be understood that other forms of shock absorbing devices may be employed but the specic structure described has been found to be very cheap in cost, simple and efiicient in function.

The shattered parts of the firing head if not completely disintegrated by the explosion will remain in the hole made. A conventional reaming tool may then be run into the well bore andthe hole formed by the explosion may be reamed to smooth out the wall thereof and bring it to full dia-meter where necessary. Any cuttings and the shattered parts of the firing head may be shed out or washed out by means and methods conventional in the well drilling art. In many cases, the shattering of the ring head will be sufficiently complete that the particles thereof will not interfere with further drilling and they need not, therefore, be removed from the well bore to permit resumption of the drilling.

. This shooting operation may be repeated as often as necessary in order to extend the Well bore entirely through the hard formation. Where a metallic object, such as a bit cone, has lodged in the bottom of the well, the same operation may be employed to remove it, as hereinbefore described. The force of the explosive directed in the manner previously described will cut through or shatter such an object to a degree such that it will no longer present an obstacle to further drilling.

Ordinarily the diameter of the firing head including the body of the explosive charge will be vmade as near that of the bore hole as possible while still permitting the apparatus to be lowered through the bore hole without hindrance. By proper dimensioning of the angularity of hollow 28 and liner member 2li and of the spacing between the hollowed face of the charge and the object to be pierced thereby, in accordance with the principles disclosed in the aforo-mentioned applications, Serial Nos. 703,655 and 709,246, the explosive force may be concentrated into a column which will be maintained for a distance suflicient to produce a hole of the desired depth. For piercing a hard rock formation with a hole which will be of substantially the desired diameter, hollow 23 and liner member 29 may be made in the conical form illustrated, having an included angle (viewed in axial section) of from about to 100 degrees, and preferably about 90 degrees. By reducing this angle below degrecs, a more sharply tapered hole may be made, while by widening the angle above 90 degrees, the hole may even be made slightly divergent. Generally an angle of about 90 degrees will provideA outstanding characteristic ofthe methodof this invention, that the walls of' the hole made by the explosion are not appreciably shattered or cracked so that a relatively smooth bore hole will be provided through the hard formations.

Itshould be understood that liner member V29 is not intended to be, and does not function asy a projectile. It is designed to be ruptured and 2l of the carrier 20 is not designed to function as a projectile but more as a stand-off or spacer from the detonation of the chemical charge adjacent the bottom of the hole.

In addition to acting as a guide for the apparatus, nose piece 2! performs additional important functions, in that it serves as a spacer for suitably spacing the hollowed face of the charge from the formation or object to be pierced. This spacing, which may be termed the Zone of convergence, is important to permit the explosive force to be converged into the column or jet and ldevelop maximum pressure and velocity before the jet strikes the object to be pierced. The spacing is variable to suit the conditions encountered and will be determined by the angle of the hollow, the character of the liner, the mass and character of the explosive charge and the degree of penetration desired. It isl important that the zone of convergence of the explosive force be shielded against interference by extraneous ma- .,terials, so that the explosive force may be free to develop its jet or Column form. Accordingly, nose ,piece 2i also functions to seal the zone of convergence against such interference, particularly ...in the common case where the piercing operation is conducted in a bore hole containing fluid, such as weil fluids or drilling mud.

In a specific example of the application of this invention to the advancement of a well bore through a hardrock formation, the ring head Se contained a cylindrical explosive charge 2l) which was 1i inches in diameter and approxi- -mately 8 inches long, which was composed of about five pounds of the detonating explosive commonly known as Cyclonite The hollow `2S was conical in form and the included angle at the apex thereof was 90, Liner 2S was constructed of steel 0.090 inch thick. The axial disapex of nose piece 2l, that is, the zone of convergence, was four and three-quarters inches. `When run into a well to a point adjacent the formation and set off, a smooth walled hole was pierced through the hard rock. This hole had a substantially uniform diameter of approximatehT ing them to small enough fragments so that they will no longer interfere with conventional drilling, while at the same time advancing the bore hole for a substantial distance.

As one example of the efficiency of this ernoodiinent of the present invention, a well being drilled by conventional methods encountered a lostloitcone at a depthof 7641 feet. A conveneifect vtional milling tool was run into the well and operated for twelve hours without any appreciable An apparatus in accordance with this `inventionwas then run into the well. A firing -head of l1/2 inchO. D. containing only 4 pounds a detonating explosive, largely Cyclonita drilling.

was runI into the well and set oif. Not only was the bit cone completely destroyed but the well bore was advanced approximately three feet. A

conventional rock bit was then run into the well and normal drilling resumed without further difnculty. .Less than two hours time was required for the shooting operation. In this instance a conical liner `having an angle of 9D degrees was employed and the spacing of the charge from the object, that is, the zone of convergence, was about 5 inches.

Fig. 8 illustrates the application of this invention to another condition frequently encountered in well drilling. In this case, due to certain conditions well known in the drilling art, a new section of. bore hole must be drilled at an angle to the vertical axis of the original bore hole. This is commonly known as off-set or whip-stock In this type of drilling an opening or window E54 must be cut in the side of the well casing lieto provide access to the surrounding earth formations. Conventionally, a tool, indicated by the numeral Sli, commonly known as a whipstoclr is set in casing B2 at the desired depth. The whip-stock is provided with a sloping face which is adapted to guide the drilling tools ,bit will be substituted for the cutting tool and Y guided by the whip-stock, will proceed to drill tance from the lower end of the hollow to the yapplication Serial Number 709,246.

, bottom of bore t3.

the off-set bore hole, indicated by the numeral 63. The window may however be cut by a concentrated gaseous penetrating jet, as described in Should the earth formations immediately outside the window be of very hard character, or if the window cutting tool or other tool should be broken and drop a hard metal part in bore E53 just below the window, as frequently occurs in this type of drilling, it becomes extremely diiicult to advance the new well bore by means of conventional tools. In such a case, this invention may be successfully employed to overcome such difficulties. In accordance with this invention and as illustrated in 8, a firing head il?, will be lowered along the face of whip-stock @il and directed against the When fired, in the manner previously described, bore 63 will be advanced .through the hard formation or extraneous hard object for a sunicient distance so that drilling may be resumed by the more conventional methods.

The apparatus of this invention may be opl erated successfully at any depth in wells which are dry or contain fluids. By the apparatus of .this invention, extremely hard earth formations or extraneous metallic objects may be readily pierced in a fraction of the time and at a fraction of the cost required by more conventional methods.' When shale is encountered, particularly of the heaving or sloughing type, this shale will-be penetrated. in an efficient manner.

t will be understood that various changes and alterations may be made in the details of the apparatus in accordance with this invention without departing fromthe scope of the appended claims but within the spirit of this invention.

9 What I claim and desire to secure by Letters Patent is:

1. An apparatus for advancing a well bore through a hard object in the well bore, comprising, a tubular casing designed and dimensioned for placement in the well bore on a cable, a recoil-absorbing element connected between said casing and said cable, said recoil-absorbing element comprising an elongated ilexible metallic tube, a charge of a detonating explosive in said casing, a generally conical hollow in the lower end of said charge, a correspondingly hollowed liner member lying against said hollow, said hollow being vertically spaced from the lower end of said casing, and means to detonate said charge.

2. An apparatus for advancing a well bore through a hard object in the well bore, comprising, a tubular casing designed and dimensioned for placement in the well bore, said casing being closed at its lower end and having aremovable closure for its upper end, a charge of a detonating explosive enclosed within said casing and having its lower end spaced from the closed lower end thereof, a downwardly facing generally conical hollow in the lower end of said charge, a liner member of correspondingly hollowed shape lining the face of said hollow, a fuse element arranged in said removable closure in detonating relation to said charge, a recoil-absorbing element connecting said casing to a cable, said element comprising a flexible metal tube, and means for setting-off said fuse element.

3. An apparatus for advancing a well bore through a hard object in the well bore, comprising, a tubular casing insertible in the well bore, said casing having a closed downwardly con- 'verging conical nose portion closing its lower end, an upwardly facing annular shoulder inside said casing vertically spaced above said nose portion, a charge of a detonating explosive enclosed within the portion of said casing above said shoulder, a downwardly facing generally conical hollow in the lower end of said charge,

10 a thin metallic liner conforming in shape to and seated within said hollow, the base end of said liner being seated on said shoulder, a closure ,member removably connected to the upper end of a lowering cable, and means for conducting electric current from said cable through the bores of said tube and said sleeve to said detonating element.

References Cited in the le of this patent UNITED STATES PATENTS OTHER REFERENCES The Shaped Charge, by Volta Torrey, pages 16o-163 incl. of the Explosives Engineer, July- August 1945. (Copy in Div. 49.)

'I'he Shaped Charge by Huttl, from Engineering and Mining Journal, May 1946, pages 58 through 63. Copy in Div. 70.

Industrial Application of Shaped Charges, by Lawrence, The Explosives Engineer, November- December 1947, pages 171-173, 182 and 183. Copy in Div. 70. 

